The present invention relates generally to the synthesis of the insensitive high-explosive triaminotrinitrobenzene. (TATB) and, more particularly, to the synthesis of ultrafine TATB by sonochemical amination.
The compound 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is an explosive having a high melting point and thermal stability that has been applied in situations where insensitivity to impact hazards is important. In the past, production-grade TATB was prepared by amination of 1,3,5-trichloro-2,4,6-trinitrobenzene (TCTNB) in toluene with anhydrous ammonia gas in a pressurized reactor. TATB thus produced is suitable for most applications requiring a particle size ranging from 30-60 xcexcm. However, for applications requiring higher sensitivity to shock initiation, fine-grained TATB is desirable. Ultrafine TATB is generally considered to be TATB having a particle size under 10 xcexcm. Unfortunately, the processes involved for the production of such ultrafine TATB (UF-TATB) are complicated and time consuming.
Ultrasound includes sound frequencies beyond human hearing; that is, above 16 kHz. When ultrasound is applied to liquids of either a homogeneous or heterogeneous reaction system, acoustic cavitation results. Rate enhancement of chemical reactions accompanied by higher production yields has been demonstrated under the influence of ultrasonic irradiation (ultrasonication).
In xe2x80x9cSynthesis And Characterization Of Sonochemically Aminated 1,3,5-Triamino-2,4,6-Trinitrobenzenexe2x80x9d by Julie Bremser et al., J. Energetic. Materials 17, 297 (1999), the preparation of TATB from TCTNB in toluene by amination with ammonium hydroxide solution under the influence of ultrasonic irradiation is described. The room-temperature reaction was initiated by immersing the sonicator horn of an ultrasonic liquid processor operating at 20 kHz into a vessel containing a two-phase solution of TCTNB in toluene and ammonium hydroxide. A piece of aluminum foil was used to cover the vessel in order to avoid the escape of a significant amount of ammonia gas. After 40 min. of sonication, the resulting emulsion was allowed to stand overnight at ambient temperature. The TATB precipitate was collected by filtration, washed sequentially with hot water, toluene and acetone, and dried at 98xc2x0 C. in a vacuum oven overnight. Although the arithmetic median diameter of the TATB particles produced by this method was approximately 15 xcexcm, the TATB was found to be slightly more sensitive to shock initiation than the approximately 5 xcexcm median diameter micronized (fluid energy mill) UF-TATB prepared using established methods.
Accordingly, it is an object of the present invention to provide a method for preparing TATB having improved sensitivity to shock initiation over that for ultrafine TATB prepared by other methods.
Additional objects, advantages and novel features of the invention will be set forth, in part, in the description that follows, and, in part, will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects of the present invention, and in accordance with its purposes, as embodied and broadly described herein, the method for producing triamino-trinitrobenzene hereof includes ultrasonically mixing a solution of trichloro-trinitrobenzene in a solvent therefor and a solution of ammonium hydroxide in a cooled, sealed vessel such that an emulsion of triaminotrinitrobenzene is formed; and separating the triamino-trinitrobenzene from the emulsion.
It is preferred that the solvent for trichloro-trinitrobenzene is toluene.
Preferably, the solution of trichloro-trinitrobenzene and the solution of ammonium hydroxide are maintained at between 1xc2x0 C. and 15xc2x0 C. during the step of ultrasonically mixing the solutions.
Benefits and advantages of the present invention include the single-step production of fine-grained triamino-trinitrobenzene (TATB) powders having improved detonation-spreading performance and hence increased shock sensitivity when compared with that for ultrafine TATB (UF-TATB).